Since the start of the digital broadcasting, various types of images including SD (Standard Definition) and HD (High Definition) images are becoming more commonly available and familiar to the public viewers.
In order to view such various types of images provided by digital broadcasting systems, an image transform is required between SD images and HD images for displaying HD images on an SD image display device and vice versa.
In general, due to the time needed to make such an image transform, video signals become asynchronous to corresponding audio signals in their reconstruction. If the image transform is performed by using a same LSI that processes the audio signals, the video signals can be synchronized to the audio signals based on, e.g., time stamps. However, in case of a system in which the image transform such as a resolution conversion is performed by using an additional image processing LSI, the video signals become asynchronous to the audio signals.
To reduce the asynchronicity between the video and the audio signal, there is proposed a system for synchronizing the audio signal to the video signal by delaying the audio signal (for example, see Japanese Laid-Open Application No. 2004-88442). In accordance with this system, the audio signal is stored in a memory, and read out therefrom after a specified time to be outputted, so that the audio signal becomes synchronous to the video signal.
However, in case the audio signal is modulated by biphase mark modulation, which is widely used for commercial equipments, 2 bits are needed for representing 1 bit audio signal because of the characteristic of the biphase mark modulation. Therefore, a large memory capacity is needed if the audio signal modulated by the biphase mark modulation is directly stored in the memory.